Microtome assembly

ABSTRACT

In a microtome which has a housing on a support a carriage adapted for forward feed and retraction movements in a horizontal plane and mounting a vertically adjustable head which supports a forwardly extending block holder adapted to mount a tissue specimen containing block adapted for vertical slicing movements with respect to a stationary knife and with each vertical slicing movement accompanied by incremental horizontal feed movement of the block towards the knife for successive slicing thereof; the improvement for said microtome which includes a block holder on the forward end of the head preformed to snugly receive the tissue block to be sliced and with a magnet for holding the tissue block within the block holder, a power operated reciprocal block support carrier and cassette for the storage of blocks to be sliced and for delivering said blocks one at a time to the block support for increment positioning with respect to the block holder and with power means for effecting automatic feed movements of the block support, an improved knife assembly with flexible blade whose ends are mounted upon feed and take-up reels for intermittent advancement, a motor for advancing the take-up reel, the power operated conveyor belt for transporting away specimen slices in a continuous manner together with a chute for delivery of partly sliced blocks to a storage chamber positioned below the block holder when retracted adapted to receive blocks when released from the block holder and including an electrical circuit connected with a series of motors and limit switches to provide for an automatic cycling operation in a continuous manner.

United States Patent" Kobernick 1451- June 6, 1972 [72] Inventor:

52 us. (:1 ..s3/9s, 83/155. 83/165,

M 511 1111. C1 ..G0ln 1 06, B26d 7 02, B26d 7/08 58 Field ofSearch ..83 98, 155, 165, 167, 170,

83/171, 201.02, 364, 367, 416, 417, 451, 648, 662, 699, 700, 926 H, 915.5; 279/1 L, 1 M; 269/8, 321

Primary Examiner-Frank T, Yost Attorney-Cullen, Settle, Slornan & Cantor [57] ABSTRACT In a microtome which has a housing on a support a carriage adapted for forward feed and retraction movements in a horizontal plane and mounting a vertically adjustable head which supports a forwardly extendingblock holder adapted to mount a'tissue specimen containing block adapted for vertical slicing movements with respect to a stationary knife and with each vertical slicing movement accompanied by incremental horizontal feed movement of the block towards the knife for successive slicing thereof; the improvement for said microtome which includes a block holder on the forward end of the head preformed to snugly receive the tissue block to be sliced and with a magnet for holding the tissue block within the block holder, :1 power operated reciprocal block support carrier and cassette for the storage of blocks to be sliced and for delivering said blocks one at a time to the block support for increment positioning with respect to the block holder and with power means for effecting automatic feed movements of the block support, an improved knife assembly with flexible blade whose ends are mounted upon feed and take-up reels for intermittent advancement, a motor for advancing the take-up reel, the power operated conveyor belt for transporting away specimen slices in a continuous manner together with a chute for delivery of partly sliced blocks to a storage chamber positioned below' the block holder when retracted adapted to receive blocks when released from the block holder and including an electrical circuit connected with a series of motors and limit switches to provide for an automatic cycling operation in a continuous manner.

18 Claims, 10 Drawing Figures PATENTEDJUH 6 I972 3,667, 330

SHEET 1 or 4 k FIG. I

37 INVENTOR SIDNEY D. KOBERNICK PATENTEDJUR 6 I972 3, 667. 330

SHEET 2 OF 4 FIG. 3

I 1P6, FIG.4 73

T ll lz/ 65 6 /35 F ;'L i Ti? INVENTOR SIDNEY 0. KOBERN ICK BY W, I {m ATTORNEYS PATENTEnJun 6 m2 3. 667, 330

sum 30F 4 FIG. 6

SOURCE -OF AIR FIG. 7

62 mvsmon $IDNEY D. KOBERNICK ATTORNEYS PATENTEDJUH 6 I972 3.667, 330

SHEET w a ATTORNEYS Microtome devices have been heretofore available by which a tissue specimen enclosed within a block of parafin is mechanically fed with respect to a stationary knife and mechanically reciprocated in a vertical plane as it is advanced towards the knife for obtaining a series of thin slices of the parafin block enclosed specimen in the nature of 3 to microns for the purpose of developing slides for microscopic analysis.

The mechanisms heretofore employed were cumbersome in structure and function, required considerable manual attention.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to incorporate into a microtome machine feed mechanism and controls with a proper circuit for effecting an automatic and continuous operation thereof.

It is another object to provide an improved tissue specimen enclosing block assembly for use in conjunction with an improved block holder for locating said block assembly and for anchoring the same upon a vertically adjustable head for and during the continuous slicing operation.

It is another object to provide an improved multiple block storage cassette in conjunction with a block load carrier and reciprocal block support adapted to intermittently feed a single block onto the said block holder and to provide means for the successive feeding of the second block once the first block has been fully sliced.

It is a further object to provide an improved knife blade construction and to provide a means for changing or incrementally feeding the knife blade from time to time so as to provide a new cutting edge together with power means for knife advance as desired.

It is a further object to provide in conjunction with the slicing device a conveyor arrangement for removing the specimen slices progressively and with air jet means for assisting the delivery of the slices onto the conveying means.

It is another object to provide block receiver for the storage of blocks that have been sliced to a predetermined extent and in conjunction with a chute whose upper open receiving end is positioned adjacent and below the block holder when in its retracted position so that blocks released from the block holder will fall by gravity into the chute.

It is a further object to provide a limit switch within said chute which when engaged by the said falling block is adapted to effect a recycling of the machine for the purpose of feeding a new block into the block holder.

It is another object to provide in conjunction with the block feeding device a carriage feeding device, a vertical feeding device, separate motors and a series of limit switches arranged in electrical circuit with a power source to accomplish an automatic operation of the microtome assembly to move through a complete cycle and succeeding cycles in a continuous manner.

These and other objects will be seen from the following specification and claims in conjunction with the appended drawings.

THE DRAWINGS FIG. 1 is a fragmentary plan view of the present microtome assembly. 2

FIG. 2 is a fragmentary secti n taken in the direction of arrows 22 ofFIG. 1. Z

FIG. 3 is a fragmentary sec on taken in the direction of arrows 3-3 of FIG. 1.

FIG. 4 is a fragmentary setion taken in the direction of arrows 4-4 of FIG. 1.

FIG. 5 is a fragmentary section taken in the direction of arrows 5-5 of FIG. 4.

FIG. 6 is a fragmentary elevational view taken on line 6-6 of FIG. 1, showing the knife assembly.

FIG. 7 is a fragmentary section taken on line 7-7 of FIG. 6.

FIG. 8 is a fragmentary perspective view of the tissue block forming apparatus.

FIG. 9 is a perspective view of a tissue specimen block.

FIG. 10 is an electrical diagram of the apparatus.

DETAILED DESCRIPTION Conventional Microtome Construction The microtome generally indicated at 10, FIG. I, in a fragmentary and schematic mannerincludes horizontally disposed support 11, mounting housing 12, there being a horizontally disposed base 13 on said housing mounting a pair of opposed parallel ways 14, which project forwardly of said housing.

Positioned within housing 12 is carriage l5 movably mounted upon said ways and including vertical guide-ways l6 guidably receiving head 18 adapted for vertical reciprocal movements upon said carriage.

The conventional microtome further includes upon said head inclined rear cam surface 19 operably engaged by cam finger 20 which projects from increment advance block 21.

Motor M2, FIG. 1, mounted on support 11 includes output shaft 23 which through slip coupling 24 or clutch is in a free wheeling drive engagement with feed screw 25, joumalled through the housing walls as at 26.

Corresponding parallel guide rod 27 extends loosely through block 21 and is anchored as at 28 upon the housing side walls to limit feed movements of block 21 to longitudinal movements with respect to the feed screw 25 to which it is threadedly connected.

Forming a part of the conventional microtome construction also is the upright slot 30 in the forward wall of housing 12. Carriage 15, FIG. 1, is spring loaded as shown at 31 and is normally biased rearwardly so that its cam surface 19 remains in engagement with cam finger 20. Accordingly, upon reversal of motor M2 causing retraction of the incremental advance block 21, said carriage will automatically retract under said spring load to its inoperative position. 1

Forming a part of head 18 and projecting forwardly thereof is a chuck 32 which tenninates at its forward end in the block holder 34, and adjacent thereto mounts electro-magnet 33. Also forming a part of the conventional microtome is motor M3, FIG. I, mounted upon support 11 which controls the vertical cutting movements of head 18; and also controls incremental advance feeding of the carriage so as to movably present the block forwardly during the continuous slicing operation. I I

The output of motor M3 includes friction roller 37 or other suitable driving means which frictionally or otherwise operatively engages cutting flywheel 38 secured upon shaft 39. The latter shaft is joumalled at 41 upon housing 12 and intermediate its ends includes an eccentric or cam 40. Said cam operatively engages the undersurface of head 18 and is adapted on rotation to effect intermittent vertical movements of head 18 with respect to its supporting carriage in a conventional manner.

Also forming a part of the conventional microtome construction is the pawl 42, FIG. 1, pivotally mounted at 43 upon head 18 with a spring bias means 44 nonnally urging said pawl into operative engagement with increment feed ratchet 47. Arrow 45, FIG. 2, illustrates the vertical path of reciprocating movement of head 18, whereas arrow 46 indicates horizontal feed movements of block holder 34.

The feed ratchet accordingly is incrementally rotated in a clockwise direction on each upward movement of the head 18. Since feed ratchet 47 is secured to feed screw 25, such incremental rotation of the ratchet will 'cause a corresponding further rotation of feed screw 25 as will cause the increment advance of block 21 to continue to feed in the same direction. This causes furtherforward incremental feed movements intermittently of carriage 15 and head assembly 18-32.

This is for the conventional purpose and function of moving the carriage and associated block holder 34 towards the cutting knife 83, FIG. 1, in such manner that successive slices of the tissue block will be made therein during. continued reciprocal vertical movements of the block holder and tissue block with respect to said cutting knife. Said cutting knife is normally a stationary cutting knife in conventional constructions, but in the present microtome is adjustable.

Since at times in conventional microtome operation it is necessary to vary the extent of incremental forward feed movements of the block depending upon the thickness of slice desired, a mechanism is incorporated into the ratchet assembly 47 for the purpose of determining the incremental rotary movement of said ratchet on each upward movement for example of the pawl 42. For this purpose there is provided a pinion 48 engagable with said ratchet mounted on adjustable shaft 49 which extends from a suitable increment advance and retard device 50, which can be so adjusted in conventional manner as to limit the exact increment of rotary adjustment of said ratchet on each operative engagement of pawl 42.

This provides a useful and convenient but conventional means by which the extent of incremental inward feed of the block specimen is controlled in a continuous and automatic manner. The increment thickness advance and retard device is generally indicated at 50, but its detail of construction is omitted since it is conventional.

Conventional microtome devices often include a power operated feed belt 51 such as shown fragmentarily in FIGS. 1, 6 and 7, connected with a drive roller 53 and motor 52 at one end and with suitable idler support 54 at its other end. Said belt is positioned longitudinally of block holder 34 and arranged adjacent knife 83 and adapted to receive the falling sliced strips from the tissued block during operation of the microtome. This is for transporting the individual block slices along said belt for collection in any suitable manner for future usage.

The foregoing description is primarily intended for background and is illustrative of conventional microtome equipment normally available on the market.

THE PRESENT INVENTION Referring to FIG. 8, there is schematically shown a portion of a multiple mold assembly 60 adapted for the molding of parafin blocks 61 which enclose a tissue specimen 62 which has been previously processed in a conventional manner. The

parafm block serves as a holder mechanism by which the 7 housing 12 and guidably positions therein a power reciprocated block carrier 66 which is positioned for transverse reciprocal movements within said housing. Means for effecting reciprocal movements of the block carrier include solenoid 67 with reciprocal rod 68 at its end connected to block carrier 66.

Block carrier-66 includes a laterally extending platform 72 which in the retracted position shown is in registry with the corresponding rectangular aperture in the top surface of guide housing 64 and a corresponding aperture which forms the bore 74 of cassette 73. The latter is in normal vertical registry with platform 72 when carrier 66 is in fully retracted position.

BLOCK HOLDER The present improved block holder 34 incluees a pair of opposed angularly related tapered walls 75 which correspond to the taper inclined walls 64 of block assembly 61, FIG. 9. When block carrier 66 has been advanced to the right of the position shown "FIG. I :by operation of solenoid 67, platform 72 KNIFE ASSEMBLY Block 78 is transversely mounted upon ways 14 and supports the transversely arranged knife guide 77, FIGS. 6 and 7. A pair of arcuate tiltable support blocks 80 is positioned adjustably upon the respective ways '14 mounting spindles 82 which journal flexible knife reels 81- and 84 mounting in spool form a continuous sharpened knife blade 83.

Said knife extends transversely along knife holder guide 77, is projected thereabove and is wound upon the knife take-up reel 84. The latter reel is secured to the rotative wonn wheel 85 in mesh with work 86 on output shaft 87 with knife advance motor 88 mounted also on support 1 1.

Motor 88 may be automatically activated and deactivated from time to time or amy be manually controlled to provide a means by which knife blade 83, of a flexible steel construction, may be advanced from time to time to present new cutting edge for the tissue block slicing operation, see FIGS. 1 and 10.

SWITCH ASSEMBLIES Micro-switch M81 is positioned upon the interior of housing 12 adapted for engagement by block 21 when it has been power returned to the inoperative position shown. Limit switch LS3 is mounted upon housing 65 intermediate the end thereof FIG. 4, in a position to be operatively engaged by block carrier 66 when it has returned to the inoperative position shown.

Limit switch LS4, FIGS. 1 and 7, is mounted upon base 11 adjacent the blade assembly 83 and in the path of forward feed movement of block holder 34; and is adapted to be activated when carriage 15 has fed the block holder and mounted tissue block into direct operative position with respect to knife assembly 83.

Limit switch LS4 is provided in the electrical circuit, FIG. 10, to accomplish the following functions:

1. On engagement deactivates motor M2 interrupting feed movement of carriage l4 and associated head 18 and block holder 34 with respect to the blade assembly 83.

2. Energizes electric motor M3 for effecting continued reciprocal vertical feed movements of the head 18 as shown by arrow 45, FIG. 2, and causing corresponding vertical feed movements of block holder 34 and the mounted tissue block assembly for movement with respect to blade 83 for cutting off slices of the tissue block which drop down onto conveyor 51.

The present improved microtome construction also includes a counter or timing mechanism by which after a predetermined number of slices of a predetermined thickness have been severed from the parafin specimen block assembly 61, motor M3 will be deactivated. Alternately, after such predetermined number of slices, motor M2, FIG. 1, may be actuated for operation in reverse causing feed screw 25 to rotate in such direction as to cause a retraction to the left of block 21 This effects a simultaneous retraction of carriage 15 and connected block holder 34. This will effect a disengagement of limit switch LS4 simultaneously deactivating vertical feed control motor M3, see FIG. 10.

When block 21 has returned to fully retracted position, it is in engagement with microswitch MSl, FIG. 1, which causes the following functions.

I. Deactivates electromagnet 33, FIG. 1.

2. Tissue block assembly 61-63 drops by gravity into the upper open end of the chute 93 and moves by gravity down the chute and into the storage compartment or receiver 94.

The upper end of the chute is positioned so as to be directly under the block holder 34 when in its fully retracted position, thus, adapted to receive the falling block holder after it has been released on deactivation of electro-magnet 33.

AIR JET ASSEMBLY Referring to FIG. 7, in conjunction with the function and operation of knife assembly 83, there is provided adjacent thereto an air conduit 95 adapted for connection to a source of compressed air 96. Air jet outlet 97 is arranged upon the end of said conduit and is positioned so as to provide downward stream of compressed air adjacent and directly above knife 83 in order to facilitate dropping of the individual slices from the tissue block onto conveyor belt 51.

Since these slices from the parafm block are relatively thin in the range of three to five microns, for illustration, the jet of air assists in separating the slice from the block after it has been severed so that it falls onto the conveyor belt 51, fragmentarily shown in FIG. 7.

OPERATION With respect to FIG. I and the diagram FIG. 10, the cycle of operation of the present improved microtome assembly is as follows. There is shown schematically in FIG. 10, an electrical circuit 99 connected to a power source 100 and including an off and on switch 98 for initiating the cycle.

With the circuit closed, solenoid 67 is energized. Block carrier 66 mounts a single block assembly 61 upon its platform 72. Movement of the carrier to the extreme righthand position with respect to housing 65 positions block assembly 61 in cooperative registry with block holder 34 and activates limit switch LS2, FIG. 4, which in turn energizes electro-magnet 33, FIG. 1, anchoring the tissue block assembly within the block holder.

LS2 further functions to deactivate solenoid 67 causing retraction of block carrier 66 to the inoperative position shown in FIG. 1 to move it into engagement with limit switch LS3. (135 ofFIG. l0).

LS2 energizes forward feed motor M2 so that the cam finger 20 feeds the carriage assembly and associated head 18 longitudinally forward and effects a simultaneous forward feed movement of the magnetic chuck and block holder 34 towards the knife assembly 83, FIG. 1.

Properly presented forwardly with respect to the knife assembly, block holder engages limit switch LS4 which deactivates motor M2 interrupting further forward feed; at the same time energizes motor M3 to initiate the vertical adjustments of the block holder 34 and block with respect to the knife assembly 83. Some means must be provided for incrementally feeding block holder forwardly after each slice so that the block assembly is properly positioned with respect to the knife for subsequent slices. This is accomplished by the pawl and ratchet incremental feed arrangement shown in FIG. 1 elements 42, 47, 49 and 50.

In operation it is determined by either a timer or by a counting device FIG. 10 after a predetermined number of slices have been removed from the block assembly, motor M2 is actuated for operation of its output shaft in reverse direction. This begins the retraction of the head 18 and associated block holder 34 disengaging from limit switch LS4 which automati cally deactivates vertical feed control motor M3.

When the block holder has returned to its fully retracted position, block 21 has moved into engagement with microswitch M81 and produces the following additional functions:

1. Electromagnet 33 is deactivated.

2. Tissue block assembly 63 drops by gravity into the open end of the chute 93 and moves by gravity down into the receiver 94.

DETAILED OPERATION A temperature control housing is employed providing a refrigerated chamber or housing enclosing the block storage and slicing mechanism of FIG. 1. Referring to FIG. 10 cooler 127 maintains 40 to 60 F. temperature and includes a blower and motor assembly. Thermostatic control switch 131 at a preset temperature, actuates relay switch 4-CR and this locks in 4-CR-2 and activates machine function through 4CRl.

Altemately energizing of the machine may be accomplished by manual switch 133 by which relay 4-CR is activated independent of thermostatic switch 131.

A block available" normally open switch 135,LS3 is positioned at the base of cassette 73. This energizes time delay relay lTD with contact l-TD-l which has instant make and time delay break, FIG. 10.

Time delay is provided so that machine is not shut down before a new block 61 feeds into block carrier 66.

1-TD-1 connects LS2 which is normally open and closes by engagement of block 61 therewith.

LS2 is connected to 1-CR which includes 1-CR-1 to energize solenoid coil 67.

Its armature 68 projects outwardly moving block carrier 66 and block 61 into registry with block holder 34.

At this time, LS2 is mechanically moved to a second position and opens the circuit to l-CR which releases solenoid coil 67 through opening of 1-CR-1, and at the same time, energizes holding magnet 33 through 1-CR-1, FIG. 10.

LS2 in its second position turns on block loaded light 137 on the machine front panel. Now with LS2 engaged power is directed through circuit lead 141 to LS4 and to feed advance motor M2. Carriage l5 feeds forward until it engages LS4 FIG. 1 and thus, moves its contact to a second position which through lead 143 energizes S-CR. This closes 5-CR-1 at top of FIG. 10 to actuatepulse motor M3 (DC). Its speed may be varied by an external resistance'as at pulse frequency I.

In FIG. 1 incremental infeeding for slices may be mechanically accomplished by pawl 42 and ratchet wheel 47 to rotate feed screw 25 independent of M2. It is contemplated that in place of said pawl and ratchet 4247, the circuit may provide for intermittent energization of motor M2 to accomplish the same result. Such electronic control is generally shown in FIG. 10 within the block designated 145.

Motor 52 is energized at the same time as M3 to start feed of belt 51 to remove tissue slices.

Said motor 52 may operate continuously or it may be intermittently actuated under by a control switch at 147. If switch element 147 stays in the position shown, motor 52 operates continuously. If switch element 147 is cammed intermittently out of contact by operation of fly wheel 38 then motor 52 is intermittently energized.

Trim counter control relay 149, FIG. 10, responds to vertical cutting movements of the block and after a preset number of trim slices, actuates 2-TD which energizes 2-TD-2 to operate the section counter control relay 151.

In the situation where M2 is to be operated for automatic in cremental feed, then the control block 145 including contacts 2-TD-l functions. The resistance in the field of motor M2 can be adjusted to regulate speed of motor M2 and consequently the slice thickness. The trim slices may be .0005", for example, and the slice section may be the same thickness or thinner by regulating the section thickness resistance shown in bloc 145 FIG. 10.

When the number of sections has been counted out and 3-TD actuated 3-TD-l, (lower left FIG. 10), 2-CR activates 2-CR-3, reverses feed advance motor M2 until back travel closes MS-l switch which deactivates 2-CR which deactivates magnet 33 and block drops by gravity into chute 93.

In a situation where belt motor 52 is not intermittently operated, 2-CR-2 (FIG. 10 lower left) actuates motor 52 for continuous feed of belt 51.

vance control 145.

During retraction of block 21, Z-CR-l (top left FIG. has been maintained open. It closes when MS-l is actuated. This allows machine to recycle to actuate 1-CR and in turn, solenoid 67 assuming a block is available.

Block 153 in FIG. 10, provides control to energize knife advance motor 88 which may be manual or automatic.

A manua'lcontrol switch is shown at 155 connected to 6-CR to close switch G-GR-I (top right FIG. 10) to pulse motor M3; 6-CR-2 to manual trim counter 149, and 6-CR-3 to feed ad- Manual control switch 157 is adapted to close 7-CR and energize 7CR-l to pulse motor M3, 7CR2 to section counter 149, 7-CR-3 to feed advance control 145 to motor M2.

Having described my invention, reference should now be had to the following claims.

lCLAlM:

-l. In a microtome having a support, an apertured housing thereon having longitudinal ways, a reciprocal carriage on said ways, spring biased outwardly toward. inoperative position, a vertically adjustable head guidably mounted on the carriage and mounting a forwardly extending block holder which movably projects from said housing, power means to feed the carriage inwardly into operative position locating said head for reciprocal vertical movements with respect to a knife assembly upon said support, said head mounting a block of chilled paraflin enclosed tissue progressively movable across said knife assembly with means to effect continuous vertical movements of said head;

' the improvement which comprises: the formed block holder on the forward end of said head including a pair of angu- 7 larly related upright backing walls; a metallic block cover joined to said block extending along one upright edge thereof and including a pair of similarly angularly related walls adapted for registry with said block holder walls; 7 1 and magnetic means on said block holder for retaining said block thereon. v 2. In the microtome of claim 1, a horizontally disposed elongated guide housing of channel form mounted upon said housing and extending transversely of said head and laterally aligned" with said block holder walls when said head is retracted;' 1

a reciprocal block'carrier within said guide housing adapted when retracted to receive a single tissue block and when advanced to position said block within said block holder;

and. an upright tubular cassette upon and overlying said guide housing adapted to store a stack of tissue blocks and to feed them one at a time into said guide housing and upon said block carrier.

3. In the microtome of claim 2, power means adapted to effect reciprocal movements of said block carrier.

4. In the microtome of claim 3, said power means including a solenoid having a reciprocal core connected to said block carrier. 5. In the microtome of claim 2, said power means for feeding said carriage including a feed screw; Q a motor having a drive connected to said screw for rotation in one direction to efiect outward feeding of said carriage and the opposite direction to permit retraction thereof; and an electrical circuit connected to a power source and including a normally closed limit switch LS3 mounted on said guide housing in the path of return movement of said block carrier to automatically actuatesaid carriage feed motor(M2). 1 6. In the microtome of claim 2, a limit switch (LS2) on said block holder in-the path of forward movement of said block carrier engageable. thereby on positioning of the block within said block holder energize said magnetic means and successively reverse said power means to retract said block carrier to engage limit switch (LS3). 7. In the microtome of claim 6, power means (M3) for effectingcontinuous reciprocal vertical movement of said verti- 8 cally adjustable head;

and a limit switch (LS4) adjacent said knife in the path of forward feed movement of said block holder and engageable thereby to deactivate said carriage feed power means; (M2) and to energize the power means (M3) causing said block to reciprocate in a vertical plane in operative engagement with said knife.

8. ln the microtome of claim 7, said microtome including an increment advance feed mechanism controlled by vertical movement of said head connected to said carriage control feed screw to effect incremental advance feed movements of said carriage and head to permit continued slicing of said block for a predetermined number of slices;

after which power means (M2) is automatically reversed to retract said head to inoperative position and to deactivate power means (M3).

9. In the microtome of claim 8, a switch (MSl) on said housing actuated when said head and carriage is retracted to inoperative position;

7 said switch when actuated adapted to deactivate said magnetic means; (33) a downwardly inclined chute arranged below said support, a

block storage compartment at the lower end of the chute;

the upper open end of the chute being positioned directly below the block holder when fully retracted;

a partly sliced block in said block holder on deactivation on said magnetic means adapted'tofall by gravity into and through said chute. s

10. In the microtome of claim 1, said knife assembly including a upright knife guide block mounted on said support spaced from said housing and extending transversely of the block holder axis;

and an elongated upright knife blade mounted upon said support bearing against and extending above said guide block on the side thereof adjacent said block holder.

11. In the microtome of claim 10, said blade being flexible with its respective ends coiled around spaced feed and take-up reels joumalled upon vertical axes on said support and arranged outwardly of the ends of said guide block respectively.

12. In the microtome of claim 11, the mounting of said spools including support. blocks respectively positioned adjustably upon said support ways. I 1

13. In the microtome of claim 11, power feed means on said support connected with said take-up reel to intermittently advance said blade.

14. in the microtome of tiltable blocks;

a spool joumalled on each block respectively;

a guide support for each block adjustably positioned in said base ways, wherebyspools may be angularly adjusted for determining the plane of the cutting blade.

15. In the microtome of claim 10, an elongated power operated conveyor belt mounted on said support extending from said knife guide in longitudinal registry with said block holder for transporting the slices from said tissue block.

16. In the microtome of claim 15, an air supply conduit adapted for connection to a source of compressed air;

and a jet outlet on said conduit positioned above and adjacent said knife to assist loading of block slices onto said conveyor.

claim 13, a pair of spaced arcuate 17. In the microtome of claim 1, a block storage receiver positioned below said support; and a block chute inclined downwardly and outwardly, at its lower end connected to said receiver and with its upper open end being spaced below the forward end of said head adapted to receive by gravity a tissue block from said block holder upon deactivation of said magnetic means.

18. In the microtome of claim 1, a temperature controlled housing on said support and enclosing said block holder and knife assembly, and an adjustable cooling means in said latter housing preset for maintaining a predetermined reduced temperature to facilitate slicing.

* s =0: 1- s v 

1. In a microtome having a support, an apertured housing thereon having longitudinal ways, a reciprocal carriage on said ways, spring biased outwardly toward inoperative position, a vertically adjustable head guidably mounted on the carriage and mounting a forwardly extending block holder which movably projects from said housing, power means to feed the carriage inwardly into operative position locating said head for reciprocal vertical movements with respect to a knife assembly upon said support, said head mounting a block of chilled paraffin enclosed tissue progressively movable across said knife assembly with means to effect continuous vertical movements of said head; the improvement which comprises: the formed block holder on the forward end of said head including a pair of angularly related upright backing walls; a metallic block cover joined to said block extending along one upright edge thereof and including a pair of similarly angularly related walls adapted for registry with said block holder walls; and magnetic means on said block holder for retaining said block thereon.
 2. In the microtome of claim 1, a horizontally disposed elongated guide housing of channel form mounted upon said housing and extending transversely of said head and laterally aligned with said block holder walls when said head is retracted; a reciprocal block carrier within said guide housing adapted when retracted to receive a single tissue block and when advanced to position said block within said block holder; and an upright tubular cassEtte upon and overlying said guide housing adapted to store a stack of tissue blocks and to feed them one at a time into said guide housing and upon said block carrier.
 3. In the microtome of claim 2, power means adapted to effect reciprocal movements of said block carrier.
 4. In the microtome of claim 3, said power means including a solenoid having a reciprocal core connected to said block carrier.
 5. In the microtome of claim 2, said power means for feeding said carriage including a feed screw; a motor having a drive connected to said screw for rotation in one direction to effect outward feeding of said carriage and the opposite direction to permit retraction thereof; and an electrical circuit connected to a power source and including a normally closed limit switch LS3 mounted on said guide housing in the path of return movement of said block carrier to automatically actuate said carriage feed motor (M2).
 6. In the microtome of claim 2, a limit switch (LS2) on said block holder in the path of forward movement of said block carrier engageable thereby on positioning of the block within said block holder energize said magnetic means and successively reverse said power means to retract said block carrier to engage limit switch (LS3).
 7. In the microtome of claim 6, power means (M3) for effecting continuous reciprocal vertical movement of said vertically adjustable head; and a limit switch (LS4) adjacent said knife in the path of forward feed movement of said block holder and engageable thereby to deactivate said carriage feed power means; (M2) and to energize the power means (M3) causing said block to reciprocate in a vertical plane in operative engagement with said knife.
 8. In the microtome of claim 7, said microtome including an increment advance feed mechanism controlled by vertical movement of said head connected to said carriage control feed screw to effect incremental advance feed movements of said carriage and head to permit continued slicing of said block for a predetermined number of slices; after which power means (M2) is automatically reversed to retract said head to inoperative position and to deactivate power means (M3).
 9. In the microtome of claim 8, a switch (MS1) on said housing actuated when said head and carriage is retracted to inoperative position; said switch when actuated adapted to deactivate said magnetic means; (33) a downwardly inclined chute arranged below said support, a block storage compartment at the lower end of the chute; the upper open end of the chute being positioned directly below the block holder when fully retracted; a partly sliced block in said block holder on deactivation on said magnetic means adapted to fall by gravity into and through said chute.
 10. In the microtome of claim 1, said knife assembly including a upright knife guide block mounted on said support spaced from said housing and extending transversely of the block holder axis; and an elongated upright knife blade mounted upon said support bearing against and extending above said guide block on the side thereof adjacent said block holder.
 11. In the microtome of claim 10, said blade being flexible with its respective ends coiled around spaced feed and take-up reels journalled upon vertical axes on said support and arranged outwardly of the ends of said guide block respectively.
 12. In the microtome of claim 11, the mounting of said spools including support blocks respectively positioned adjustably upon said support ways.
 13. In the microtome of claim 11, power feed means on said support connected with said take-up reel to intermittently advance said blade.
 14. In the microtome of claim 13, a pair of spaced arcuate tiltable blocks; a spool journalled on each block respectively; a guide support for each block adjustably positioned in said base ways, whereby spools may be angularly adjusted for determining the plane of the cutting blade.
 15. In the microtoMe of claim 10, an elongated power operated conveyor belt mounted on said support extending from said knife guide in longitudinal registry with said block holder for transporting the slices from said tissue block.
 16. In the microtome of claim 15, an air supply conduit adapted for connection to a source of compressed air; and a jet outlet on said conduit positioned above and adjacent said knife to assist loading of block slices onto said conveyor.
 17. In the microtome of claim 1, a block storage receiver positioned below said support; and a block chute inclined downwardly and outwardly, at its lower end connected to said receiver and with its upper open end being spaced below the forward end of said head adapted to receive by gravity a tissue block from said block holder upon deactivation of said magnetic means.
 18. In the microtome of claim 1, a temperature controlled housing on said support and enclosing said block holder and knife assembly, and an adjustable cooling means in said latter housing preset for maintaining a predetermined reduced temperature to facilitate slicing. 